The British government will undertake a review of the coronavirus vaccine recently introduced by AstraZeneca as questions arise about its claimed effectiveness, the Associated Press reports.

AstraZeneca and Oxford University, its partner in development, acknowledged that the primary positive results were based on a dosing error for the medication.

The company reported that the drug was 62% effective in a group of 2,741 volunteers after one dose followed by another dose three weeks later.  The results improved significant, to 90%, when 8.895 participants received a half-dose first, followed by a full dose weeks later.

In the trial, the drugmaker stated that their primary results were based on averaging the two pools, reporting that the vaccine was 70%, a non-standard way of reporting results, particularly when the sizes of the groups were vastly different.

“They will make an assessment with lots of data that is not currently public domain on efficacy and on safety,” said England’s Chief Medical Officer, Chris Whitty.  “I think it’s always a mistake to make too many judgements early before we have the full information and particularly before the regulator, the independent regulator, has had their chance to look at the data and make an assessment.”

Both Pfizer and Moderna have reportedly developed vaccines that are around 95% effect, but the AstraZeneca version has an advantage in that it doesn’t have to be stored at sub-zero temperatures to remain effective.